|1. Insect responses to recent climate change are well documented, but the role of resource
specialization in determining species vulnerability remains poorly understood. Uncovering
local ecological effects of temperature change with high-quality, standar dized data provides
an important ?rst opportunity for predictions about responses of resource specialists, and
long-term time series are essential in revealing these responses.
2. Here, we investigate temperature-related changes in local insect communities, using a
sampling site with more than a quarter-mi llion records from two decades (1992–2009) of full-
season, quantitative light trapping of 1543 species of moths and beetles.
3. We investigated annual as well as long-term changes in fauna composition, abundance and
phenology in a climate-related context using species temperature af?nities and local tempera-
ture data. Finally, we explored these local changes in the context of dietary specialization.
4. Across both moths and beetles, temperature af?nity of specialists increased through net
gain of hot-dw elling species and net loss of cold-dwelling species. The climate-related compo-
sition of generalists remained constant over time. We observed an increase in species richness
of bot h groups. Furthermore, we observed diverg ent phenological responses between cold-
and hot-dwelling species, advancing and delaying their relative abundance, respectively.
Phenological advances were particularly pronounced in cold-adapted specialists.
5. Our results suggest an important role of resource specialization in explaining the composi-
tional and phenological responses of insect communities to local temperature increases. We
propose that resource specialists in particular are affected by local tempe rature increase, lead-
ing to the distinct temperature-mediated turnover seen for this group. We suggest that the
observed increase in species number could have been facilitated by dissimilar utilization of an
expanded growing season by cold- and hot-adapted species, as indicated by their oppositely
directed phenological responses. An especially pronounced advancement of cold-adapted spe-
cialists suggests that such phenological advances might help minimize further temperature-
induced loss of resource specialists.
6. Although limited to a single study site, our results suggest several local changes in the
insect fauna in concordance with expected change of larger-scale temperature increases|